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Methods used for deaths by suicide in New Zealand

1997–2012, number of people

About this data

Notes

For a full description of intentional self-harm categories and codes see Table A1 in the Ministry of Health publication "Suicide facts: Deaths and intentional self-harm hospitalisations 2012."

Definitions

Intentional self-harm codes and definitions:
For the years 2000–2012, The International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Australian Modification (ICD-10-AM) codes used for mortality and hospitalisation data were X60–X84: Intentional self-harm (National Centre for Classification in Health 2008)

Hospitalisations for intentional self-harm: It is important to note that hospitalisations for intentional self-harm represent individual events of self-harm rather than individual people; that is, a single person can contribute multiple unique intentional self-harm events to the data set or be hospitalised more than once for the same self-harm event.

Admission: The process by which a person becomes a resident in a health care facility. For the purposes of the Ministry of Health’s national collections, health care users who receive assessment and/or treatment for three hours or more, or who have a general anaesthetic are to be admitted. This also applies to health care users of Emergency Departments. ‘Assessment/treatment’ is clinical assessment, treatment, therapy, advice, diagnostic or investigatory procedures from a nurse or doctor or other health professional.

Ethnicity: There are different methods for outputting ethnicity data. This report uses ‘prioritised ethnicity’, where each person represented in the data is allocated to a single ethnic group using the priority system Māori > Pacific peoples > Asian > European/Other (Ministry of Health 2004). The aim of prioritisation is to ensure that, where it is necessary to assign people to a single ethnic group, ethnic groups that are small or important in terms of policy are not swamped by the European ethnic group. This is a more robust method of dealing with the low rate of multiple ethnicities in health-sector data.

Rate: The rate of suicide or intentional self-harm hospitalisations refers to the frequency with which these events occur relative to the number of people in a defined population and a defined time period.
Age-specific rates measure the frequency of suicides per 100,000 population relative to particular population age groups. Age-standardised rates per 100,000 population were standardised to the WHO world standard population

Limitations of the data

It is important to recognise that the motivation for intentional self-harm varies, and therefore hospitalisation data for self-harm is not a measure of suicide attempts.

For data comparability purposes, the total number of self-harm hospitalisations excludes two categories of patients:
1. Patients discharged from an emergency department after a length of stay of one day or less.These events were reported very differently across the individual DHBs between 2003 and 2012.
2. Patients admitted for an intentional self-harm incident within two days of a previous intentional self-harm hospitalisation. It is not unusual for patients to be transferred between hospitals after an intentional self-harm event. DHBs record these transfers as new admissions. Such admissions usually occur within two days of a previous hospitalisation discharge, thereby artificially inflating the numbers of recorded admissions.
Therefore the intentional self-harm hospitalisations data in this report does not represent the total number of people receiving hospital treatment for intentional self-harm or treatment events. Even once consistency issues between DHBs have been addressed, the total extent of intentional self-harm will still be difficult to capture because many people who intentionally self-harm do not seek hospital treatment.

A cautious approach is recommended when comparing international suicide statistics because many factors affect the recording and classification of suicide in different countries, including the level of proof required for a verdict; the stigma associated with suicide; the religion, social class or occupation of victims; and confidentiality. As a result, deaths that are classified as suicide in some countries may be classified as accidental or of undetermined intent in others.

Caution is advised when interpreting rates derived from small numbers as they may fluctuate markedly over time. This may apply to both small numbers of cases and/or small population groups.

Dataset originally released on:

October 13, 2015

Purpose of collection

The purpose of this report is to present numbers, trends and demographic profiles of people who die by suicide or seriously harm themselves. Understanding this data is important for policy makers, clinicians and others who work to prevent suicide and intentional self-harm.

Method of collection/Data provider

Data sourced from the New Zealand Mortality Collection and the New Zealand National Minimum Dataset.